Cancer cells undergo dramatic changes in carbohydrate expression during the onset and progression of disease. Unfortunately, little is known about how these changes contribute to the disease. Moreover, efforts to exploit these changes for the development of diagnostics, tumor targeting agents, or vaccines have had only limited success. One of the key limitations is the inability to evaluate the specificity of carbohydrate-protein interactions in a rapid and comprehensive manor. We are developing a carbohydrate microarray to address this issue. A carbohydrate microarray contains many different carbohydrate antigens/epitopes immobilized onto a glass microscope slide. Using an array, one can quickly analyze binding of antibodies, lectins, viruses, toxins, or cells to many different potential carbohydrate ligands simultaneously. Development of the array involved three key steps: fabrication of the arrays, development of an assay to evaluate binding, chemical synthesis of a broad range of carbohydrate ligands such as carbohydrate tumor antigens, blood group antigens, and lewis antigens for the array. We have successfully generated a carbohydrate microarray and assay. Our current generation microarray contains 73 different components. We will continue to expand and improve the array.